1. Field of the Invention
The present invention generally relates to small planing personal watercraft powered by four-cycle engines, and, more particularly, to fuel delivery for such watercraft.
2. Description of Related Art
In recent years, four-cycle engines have been proposed to improve exhaust emissions in small planing personal watercraft which are typically operated by a rider straddling a seat and steering with handlebars.
However, precise fuel delivery is required in order for four-cycle engines to produce clean exhaust. In the past, carburetors have generally been used to supply fuel to engines used in small planing watercraft. Both float-type carburetors having a float chamber, and so-called floatless carburetors using a pump integrated with the carburetor to deliver fuel to the carburetor air intake passage have been used. To control a throttle valve in the carburetor a throttle control cable wound over a throttle control sheave is typically used.
However, when floatless carburetors are used, depending on the way the fuel lines are connected to the fuel pump and the positioning of a sheave around which the throttle control cable is wound, it is difficult to maintain precise control of the fuel delivery and maintenance access to the carburetor area can be limited. For example, the fuel line may be in direct contact with, or routed around, peripheral equipment so that when making adjustments to the carburetor, the throttle cable may accidentally become crimped, or its position may inhibit performing carburetor adjustments to adjust the fuel/air mixture. Furthermore, the throttle control mechanism may be obstructed by peripheral equipment, making it difficult to perform maintenance on the mechanism or proper adjustment of the carburetor.
On the other hand, when a float type carburetor is used, depending upon the orientation of the pivot axis of the float in the float bowl or chamber, unwanted fuel may flow into the float chamber when the watercraft abruptly changes position, causing the fuel level in the chamber to rise and the rate of fuel delivery to the air intake passage to be undesirably increased.